Night vision systems include image intensification and infrared imaging monoculars, binoculars, bioculars, and goggles, whether hand-held, weapon mounted, or helmet mounted. Image intensification systems are typically equipped with one or more image intensifier tubes to allow an operator to see a range of wavelengths of radiation (approximately 400 nm to approximately 900 nm). They work by collecting the tiny amounts of light, including the visible spectrum and the lower portion of the infrared spectrum, that are present but may be imperceptible to our eyes, and amplifying it to the point that an operator can easily observe the image. These systems have been used by soldier and law enforcement personnel to see in low light conditions, for example at night or in caves and darkened buildings. A drawback to image intensification systems is that they may be attenuated by smoke and heavy sand storms and may not see a person hidden under camouflage. Other devices with an image sensor capable of converting an optical image to an electrical signal can be used in low light conditions. An image sensor may be a charge-coupled device (CCD), a complementary metal-oxide-semiconductor (CMOS) active-pixel sensor, or other sensor.
Infrared imagers allow an operator to see people and objects because they emit or reflect energy in the infrared spectrum. These systems operate by capturing energy in the infrared spectrum, which may not be perceivable by the human eye, and display the scene information to a user through an eyepiece or display. These systems may capture the upper portion of the infrared spectrum (7,000-14,000 nm), which capture electromagnetic radiation emitted by objects instead of simply reflected as light. Any object that has a temperature radiates in the infrared spectrum. An infrared sensor may be a VNIR (very near infrared), SWIR (shortwave infrared), MWIR (medium wave infrared), or LWIR (long wave infrared) sensor, for example, a focal plane array or microbolometer.
Fusion systems have been developed that combine visible and infrared sensors in a single enclosure. The visible information and the infrared information may be optically or digitally fused together to provide an image that provides benefits over the visible and the infrared spectrum. Other combinations of wavebands may also be fused such as, but not limited to, VNIR and LWIR or SWIR and LWIR.
When these vision systems are handheld or mounted on a weapon or a helmet, movement of the systems, combined with any delay caused by processing of the scene data may cause viewing difficulties. These viewing difficulties may prevent a soldier or operator from easily identifying a target or comprehending information on signs.
When a vision system is mounted on a weapon, a mechanical or electronic reticle in the vision system may be boresighted with the weapon to allow an operator to fire the weapon while looking at a display, either directly or through an eyepiece. The vision systems may allow the operator to move the reticle up or down to compensate for ballistic drop as the distance to target changes or to move the reticle left or right to adjust for windage, or both.